A promising technique of producing nanostructures, i.e. structures in the order of 100 nm and smaller, is so-called nanoimprint lithography. This technique is described in the document U.S. Pat. No. 5,772,905, which is incorporated herewith by reference. In such lithography, the main steps of which are schematically shown in FIGS. 1a–d, a pattern of nanostructures is transferred from a stamp 1 to an object 2. The object 2 consists of a substrate 2a and, applied thereto, a film 2b of a polymer material (resist). After heating of the film 2b to a suitable temperature, the stamp 1 is pressed into the same (FIG. 1b). The stamp 1 is then released from the object 2 when recesses 3 of a desired depth have been formed in the layer 2b (FIG. 1c). Subsequently any remaining film in the recesses 3 is removed, for instance by etching, thereby exposing the substrate 2a. In subsequent process steps (not shown), the pattern in the film is reproduced in the substrate or in some other material which is applied to the substrate.
A device according to the above-mentioned U.S. patent for carrying out the above lithographic process comprises a first contacting means with a receiving surface for the stamp, a second contacting means with a receiving surface for the object, and a pressing means for contacting or joining the first and second receiving surfaces with each other.
The film applied to the substrate is very thin, typically 50–200 nm. For even structuring of the object, the stamp and the object must thus be mutually parallel with an accuracy of a few nanometres. In industrial applications, the object can have a diameter of about 15–30 cm, which means that the surfaces contacting each other can have a maximum angle of inclination of about 10−7 rad. A greater inclination between the stamp and the object can, in addition to uneven structuring of the object, also result in the latter being smashed. In fact the substrate is usually made of a brittle material, e.g. Si/SiO2, GaAs or InP, and the pressure exerted upon the substrate during-contacting is high, typically 4–10 MPa.
A conceivable solution to the above problems would be to fix the receiving surfaces of the device in a mutually fully parallel relationship once and for all. This requires, however, that all objects have perfect plane-parallel flat sides. For reasons of manufacture, this is not possible, and therefore the device must be adjusted for each individual object.
According to a previously suggested solution to this problem a plurality of power or pressure sensors are mounted in the receiving surface of the stamp or the object. A control unit is adapted to actively control the mutual angular position of the contacting means based on the thus measured pressure distribution. However, this is an expensive and complicated solution, which is also difficult to scale up for structuring of large objects.